1. Field of the Invention
The present invention relates to a magneto-resistance effect element which is configured such that a current is flowed in the direction perpendicular to the film surface thereof. The present invention also relates to a magnetic head, a magnetic recording/reproducing device which utilize the magneto-resistance effect element according to the present invention. Moreover, the present invention relates to a method for manufacturing a magneto-resistance effect element.
2. Description of the Related Art
Recently, the performance of a magnetic device, particularly such as a magnetic head is enhanced by means of Giant Magneto-Resistance Effect (GMR) made of a multilayered magnetic structure. Particularly, since a spin valve film (SV film) can exhibit a larger GMR effect, the SV film has developed the magnetic device such as a magnetic head and MRAM (Magnetic Random Access Memory).
The “spin valve” film has such a structure as sandwiching a non-magnetic metal spacer layer between two ferromagnetic layers and is configured such that the magnetization of one ferromagnetic layer (often called as a “pinning layer” or “fixed magnetization layer) is fixed by the magnetization of an anti-ferromagnetic layer and the magnetization of the other ferromagnetic layer (often called as a “free layer” or “free magnetization layer”) is rotated in accordance with an external magnetic field. With the spin valve film, the large MR effect can be obtained by the variation of the relative angle in magnetization between the pinned layer and the free layer.
A conventional spin valve film is employed for a CIP (Current In plane)-GMR element. In the CIP-GMR element, a sense current is flowed to the SV film in the direction parallel to the film surface thereof. Recently, attention is paid to a CPP (Current Perpendicular to Plane)-GMR element and a TMR (Tunneling Magneto Resistance) element because the CPP-GMR element and the TMR element can exhibit the respective large MR effect in comparison with the CIP element.
Recently, it was confirmed that a large MR effect with high MR ratio can be obtained from the minute coupling of Ni wires (Reference 1).
Then, the minute magnetic coupling is formed three-dimensionally so as to realize a magneto-resistance effect element with high MR ratio (Reference 2). In this case, the three-dimensional minute magnetic coupling is carried out by means of EB (Electron beam) irradiation, FIB (Focused Ion beam) irradiation or AFM (Atomic Force Microscope).    [Reference 1] Phys. Rev. Lett. 82 2923 (1999)    [Reference 2] JP-A 2003-204095 (KOKAI)
It is considered that the MR effect as described above is originated from the rapid variation in magnetization at the minute magnetic coupling points. However, if the boundaries (wall surfaces) between the minute magnetic coupling points are roughed, the current (electrons) are scattered by the wall surfaces of the minute magnetic coupling points so that the ratio of the current contributing to the MR effect is decreased when the current is flowed so as to generate the MR effect. As a result, the variation loss in resistance of the minute magnetic coupling may occur so that the magneto-resistance effect element made of the minute magnetic coupling can not exhibit the inherent variation in magnetic resistance.